In concrete and steel firecode construction it is necessary to completely block a passage through a wall that is provided to allow conduits--pipes, wires, and the like--to pass through the wall, in order that smoke, flame, and vapors generated in a fire cannot traverse the wall. Simply packing the opening around the conduits with a fireproof substance such as gypsum concrete is possible when the installation is permanent and to be sealed, but such a procedure is unacceptable in much construction where, for instance, utility chases must be capable of accepting additional conduits or must allow removal or replacement of some of the existing ones.
Such a feedthrough assembly normally is formed of the wall with the passage that extends along an axis and has a radially inwardly directed wall. At least one conduit passes axially through the passage. At least one elastomeric adapter block has an outer surface complementarily radially outwardly engaging the wall and an inner surface snugly surrounding and engaging the conduit. A tightening element presses the inner and outer surfaces of the block sealingly against the respective conduit and pushes and therefore forces the block sealingly against the conduit and passage portion.
As described in German patent No. 958,671 filed by N. Brattberg with a claim to a Swedish priority of Oct. 6, 1952 a rectangular and L-section metal frame is imbedded in a concrete wall or welded into a steel one. The rectangular opening defined by this frame is filled by a plurality of two-piece adapter blocks that are of rectangular or square outer shape with sides parallel to the normally upright sides of the frame opening, and central holes that are, for instance, cylindrical to conform to the outer surfaces of the conduits that pass through them. Solid blocks are used in locations where no conduits are provided. These adapter blocks fit snugly together to form a solid group against the horizontal lower side of the frame opening and between the two flanking upright sides once the conduits are installed. A screw-type tightening arrangement and/or a plurality of elastic shims are wedged between the horizontal upper side of the frame opening and the group of adapter blocks, compressing them together so they seal tightly. In addition this biasing system fills the remainder of the cross section of the passage. The adapter blocks are split along horizontal planes that run perpendicular to the direction they are compressed in, so that such compression effectively seals them to one another and to the respective conduits.
In my copending patent application Ser. No. 06/612,297, the passage has an outwardly flared frustoconical portion and the outer surface of the adapter block or blocks complementarily radially outwardly engages the passage portion while its inner surface snugly surrounds and engages the conduit. The tightening element is a ring engaging axially inwardly against the block in a direction opposite the flare of the frustoconical portion and pushing the block axially inward and therefore forcing the block sealingly against the conduit and passage portion.
In order to increase the effectiveness of such arrangements it is known to mix aluminum hydroxide (alumina trihydrate, Al[OH].sub.3) with the neoprene or chloroprene elastomer that makes up the adapter blocks. When heated, this material becomes Al.sub.2 O.sub.3 and water (H.sub.2 O) in an endogenic or heat-absorbing reaction. Thus this conversion absorbs heat from the area while generating steam that displaces the local oxygen, for a dual extinguishing action. As a result such a fitting not only blocks fire from passing through it, as well of course as any vapor or liquid, but also actively participates in controlling or even extinguishing the fire. In the case of a cable feedthrough, the retardant action counteracts the tendency of the insulation of the cable to burn, thereby effectively stopping the fire right at the fire wall. As a result the overall fire rating, as time for burnthrough, is increased, allowing a short fire-retardant fitting to have the same rating as a long fire-stop fitting, with a consequential saving on manufacturing costs and, in particular, molds.
It is unfortunately impossible to incorporate much of the Al(OH).sub.3 in the elastomer blocks. No matter how much is originally mixed with the material, most is lost during treatment, particular vulcanizing, of the fitting block. What is more the additive is a particularly gritty powder that must be worked and mixed with special machines. Even substituting some agent that generates foam for the powder entails a substantial loss of active material during subsequent heat-treatment of the adapter block.